Switching power converters implement a primary-side controller that controls the duty cycle of the pulse-width modulation (PWM) signal applied to the gate of the main field effect transistor (FET). In many cases, the feedback parameter for the control loop is a signal indicative of output voltage provided from the secondary side by way of an optocoupler having its light emitting diode (LED) operatively coupled to the output voltage of the power converter, and its optically driven transistor coupled to provide the signal indicative of output voltage to the primary-side controller.